Thanks for the history lesson! The tree at the top of the page explains it all. Phillips invented the pentode, RCA as a counter the Beam tetrode beacause of the kink that all tetrodes produce when the plate voltage falls below the screen (G2) voltage. IIRC the so called kinkless tetrodes. That's also why Phillips invented the power pentode because of that kink. That's how the U.S. version 6CA7 got around the patent issues.
There's an article in one of my Audio Express mags. that covers this. I'll have to dig it up.